astro-, astr- +

(Greek: star, stars, star shaped; also pertaining to outer space)

apastron (s), apastra (pl)

1. A point at which the stars of a binary system are farthest apart, as opposed to periastron, or "when a star is closest to the star it is orbiting".
2. The point at which an object, such as a planet or comet, is farthest from the star it is orbiting.

The orbits of planets moving around the sun, of satellites moving around planets, and of stars moving around each other are never circular, but they are always elliptical or rounded like an egg.

Because of such oval movements, there will be one point in the orbits of all of the astronomical bodies when they are farther apart than at any other time in their orbits; so, in the situations of two stars (binary system), this point of greatest distance is called apastron from two Greek elements: apo-, "far" and astron, "star".

1. Anyone who studies the knowledge, interpretations, and practices of ancient cultures regarding celestial objects or phenomena.
2. Someone who studies the ancient or traditional astronomies in their cultural context, utilising archaeological and anthropological evidence.

archaeoastronomy

1. The study of the knowledge, interpretations, and practices of ancient cultures regarding celestial objects or phenomena.
2. The study of ancient or traditional astronomies in their cultural context, utilising archaeological and anthropological evidence.

astro-alchemist

The study of the chemical composition and evolution of the universe.

astrobiology

1. A branch of biology concerned with the discovery or study of life on the celestial bodies or in outer space.
2. The study of the movements of heavenly bodies and how these patterns affect living systems on earth.
3. The study of the relationship of all living things to the universe.

astroblast

A cell that develops into an astrocyte or a star-shaped cell of the nervous system.

astrobolism

The result of being struck by a star.

Supposedly, the star is Sirius, the dog star; because it rises and sets with the sun during summer in the northern hemisphere, its name is associated with "dog days" usually applicable to the hottest part of the year in places north of the equator.

The dog days are those from about the middle of July to the middle of August although the exact dates vary depending on where people live.

The thought behind astrobolism was connected to an old idea that this period of summer was under a bad influence, in which dogs ran mad, the air was unwholesome, sunstroke was common, and practical work was not done because of a lack of desire by people to do anything.

astrobotanist

Anyone who studies the possibility that plants grow on other planets.

astrobotany

A branch of botany that investigates the possibility that plants grow on other planets.

astrochemistry

1. The study of the chemical elements found in outer space, generally on larger scales than the Solar System, particularly in molecular gas clouds, and the study of their formation, interaction and destruction.
2. The branch of science that explores the chemical interactions between dust and gas interspersed between the stars.

astrochronological

Pertaining to the chronology and periods of the heavenly bodies.

astrocompass

A device for determining direction by celestial observation.

astrocyte, astrocytes

A star-shaped cell of the nervous system, which provides nutrients, support, and insulation for neurons of the central nervous system; one of the major categories of neurological cells.

astrocytic

A reference to a star-shaped cell of the nervous system.

astrocytoma

A tumor made up of astrocytes or the star-shaped cells of the nervous system.